Dog agility began as an exhibition sport in Great Britain and was imported into the United States in 1977. It was patterned after equestrian events and combines handler control, agility, and confidence. An agility ring is set up with a variety of obstacles. Obstacles include jumps, tunnels, a dog walk, a teeter-totter, an A-frame, and weave poles. The ring is generally square, about 100 feet×100 feet, and fenced off from the spectators. Dogs go through the ring on a leash with a handler (basic agility), or off leash with a guiding handler (advanced agility). They are judged by their ability to correctly negotiate the obstacles in a predetermined order. The dogs are judged primarily by the correctness by which they move on and off the obstacles and by which they stop and stay on command on other obstacles. The dogs are secondarily judged by their time in completing the obstacle course. This event requires significant training of both handler and dog.
The teeter-totter is an elongated plank that rotates about a pivot point located generally in the middle of the plank. In competition, the height of the pivot above the ground is based on the size of the dog. The plank is typically 8–14 inches wide and 10–14  feet in length. Contact zones, near each end of the plank, are typically 3–4 feet long. When a dog approaches the teeter-totter, one end of the plank, either the near end or the far end, is in contact with the ground. The dog must touch the near contact zone with at least one paw, traverse the plank, and then touch the far contact zone with at least one paw before proceeding to the next obstacle. As the dog traverse the obstacle, the plank rotates about the pivot point.
FIG. 1 is a side view of a plank 4 resting on a brick 6 in accordance with the prior art. Training of a dog 2 starts off by acquainting the dog 2 to a plank 4 resting on the ground. After the dog 2 masters touching the contact zones, the trainer may elevate the middle of the plank with a brick 6, as shown in FIG. 1, to a height “H”. As the dog 2 gains more confidence, the trainer may stack additional bricks under the plank 4. A drawback to stacking bricks is that the bricks may topple while the dog 2 is traversing the obstacle and make the dog afraid of the obstacle.
Therefore, there is a need for a teeter-totter in which the pivot height of the plank can be quickly changed while still providing a secure structure.